NCT07766499 · Calixis Inc.
A Study to Assess the Efficacy and Safety of THB335 in Adults With Chronic Spontaneous Urticaria (CSU)
What this study is about
THB335-201 is a Phase 2, randomly assigned, where neither patients nor doctors know which treatment is given, compared against an inactive treatment, parallel-group, conducted at multiple hospitals study in adults with CSU who remain symptomatic despite standard-of-care treatment.
View original scientific description
THB335-201 is a Phase 2, randomized, double-blind, placebo-controlled, parallel-group, multicenter study in adults with CSU who remain symptomatic despite standard-of-care treatment. The study includes a Screening Period of up to 4 weeks, a 12-week Treatment Period, and a 4-week Follow-Up Period, for a total participant duration of approximately 20 weeks.
Interventions
DRUG
THB335 Lower Dose
THB335 is an orally administered capsule added to a stable background regimen of a second generation H1 antihistamine.
DRUG
THB335 Higher Dose
THB335 is an orally administered capsule added to a stable background regimen of a second generation H1 antihistamine.
DRUG
Placebo
Placebo is an orally administered capsule added to a stable background regimen of a second generation H1 antihistamine.
Primary outcome measures
Change From Baseline in Weekly Urticaria Activity Score (UAS7) at Week 12
Time frame: Baseline and Week 12
UAS7 is the sum of daily Urticaria Activity Scores over 7 days. The daily score combines the Hives Severity Score and Itch Severity Score, each scored from 0 to 3. UAS7 ranges from 0 to 42; higher scores indicate greater disease activity.
Who can participate
This study lists these criteria on ClinicalTrials.gov. A study coordinator reviews eligibility during screening — this page does not determine whether you qualify.
Inclusion criteria
- Males and females 18 through 85 years.
- Diagnosis of chronic spontaneous urticaria (CSU) ≥ 6 months.
- Active CSU despite treatment with a second-generation H1 antihistamine.
- Weekly Urticaria Activity Score (UAS7) ≥ 16 and ISS7 ≥ 8 during the 7 days before randomization, with sufficient electronic diary entries to calculate the baseline scores.
- Body mass index of 18 to 38 kg/m² and minimum body weight of 50 kg for male participants or 45 kg for female participants.
- Willing and able to complete the daily electronic diary, attend scheduled study visits, and comply with study procedures.
- Participants capable of becoming pregnant or producing sperm must agree to follow the protocol-defined contraception requirements. Key
Exclusion criteria
- Chronic urticaria with an identified cause other than chronic spontaneous urticaria.
- Another active skin condition associated with chronic itching that could interfere with the study assessments.
- Recent treatment with prohibited immunosuppressive therapy, biologic therapy, a Bruton's tyrosine kinase inhibitor, an investigational drug, or another therapy that inhibits the c-KIT receptor.
- Clinically significant hepatic, hematologic, or renal disease or laboratory abnormalities.
- Active, chronic, or recurrent infection, including human immunodeficiency virus or viral hepatitis infection.
- Clinically significant cardiovascular disease or electrocardiogram abnormality, including clinically significant arrhythmia, prolonged QT interval, familial long QT syndrome, or use of medication known to prolong the QT interval that cannot be discontinued.
- History of idiopathic anaphylaxis, a severe allergic reaction that may increase the risk of study participation, or hypersensitivity to the study drug or related compounds.
- History of malignancy within the previous 5 years, except successfully treated nonmetastatic basal cell or squamous cell skin cancer or carcinoma in situ.
- Current or planned use of prohibited medications, including specified inhibitors, inducers, or sensitive substrates of drug-metabolizing enzymes or transporters, or proton pump inhibitors.
- Positive urine drug screen at Screening.
- Pregnancy or breastfeeding.
- Any medical or psychiatric condition that, in the investigator's judgment, could place the participant at increased risk, interfere with the study assessments, or affect the participant's ability to complete the study. Additional eligibility criteria are outlined in the full protocol. The study investigator will review all requirements with potential participants to determine whether they are eligible to participate.
Where
- Pasadena, California
- Ventura, California
- Walnut Creek, California
- Altamonte Springs, Florida
- Tampa, Florida
- Atlanta, Georgia
- Boise, Idaho
- Baton Rouge, Louisiana
- White Marsh, Maryland
- Wildwood, Missouri
- Asheville, North Carolina
- Smyrna, Tennessee
And 3 more locations — see the full list below.
Related conditions & keywords
Frequently asked questions
What is a clinical trial?
A clinical trial is a research study that tests new medical treatments, drugs, devices, or procedures to determine their safety and effectiveness. Trials are carefully designed and monitored to protect participants while advancing medical knowledge.
Is it safe to participate?
Clinical trials follow strict safety guidelines and ethical standards. Trials must be reviewed and approved, and participants are closely monitored by medical professionals throughout the study. You can withdraw at any time if you choose.
Will I be compensated?
Many clinical trials offer compensation for your time, travel expenses, and inconvenience. The specific compensation varies by study and will be discussed during the screening process. All study-related medical care is typically provided at no cost to participants.
Will I receive a placebo instead of treatment?
When effective treatment exists, participants typically receive either the standard treatment plus the study intervention, or the standard treatment plus placebo. You would not be denied effective care. Placebos are primarily used when no proven treatment is available, or in addition to standard care. Your trial consent form will clearly explain what treatments you may receive.
Can I leave a trial if I change my mind?
Absolutely. Participation in clinical trials is completely voluntary. You have the right to withdraw from the study at any time, for any reason, without penalty or loss of benefits to which you are otherwise entitled.
How long does a clinical trial last?
Trial duration varies widely depending on the study design and purpose. Some trials last just a few weeks, while others may continue for months or years. The study coordinator will provide specific timeline information during your screening call.
Data: ClinicalTrials.gov · synced Nov 2, 2026 · Source of record for eligibility and locations